In the manufacture of various articles by use of sheet material, and in particular in the manufacture of air springs, rubberized sheet is delivered to a building drum or assembly station by various server mechanisms and systems. The majority of these stock servers as they are referred to in the industry, are deficient in that they do not compensate for stock skew and misalignment. Cutting positions are generally determined by the operator's visual reference and similar means for marking the approximate position where a manual cut is made by the operator. Dancer bars or free loops are techniques used to supply the rubberized sheet to the operator who manually pulls an estimated amount of rubberized sheet onto the building drum from the stock supply, during which, the server system automatically advances the rubberized sheet for subsequent use by the operator.
Although these prior servers are satisfactory for most applications, it is desirable to provide a server system enabling greater accuracy in delivery of sheet material to the operator to eliminate guess work on behalf of the operator in providing the correct length of sheet material to be used for placement on the drum, table or other assembly device. Furthermore, it is desirable to automate various parts of the manufacturing procedure to reduce installer error and to provide increased speed and efficiency in the manufacture of the air spring or other articles.
It is also a problem with existing servers to provide correct alignment to ensure that the delivered stock, especially at higher delivery rates, is properly aligned for subsequent cutting and placement at the assembly station. Heretofore, most prior art alignment systems required complicated positioning rolls and edge detection devices which physically contacted the moving strip, usually the longitudinal edge thereof. These edge detecting mechanisms occupy valuable space adjacent to the building drum and increase the cost of the server system and can distort the rubberized sheet due to the necessary guiding for correct positioning of the strip.
Another problem with prior art server systems, especially of the type wherein the liner is used as a control parameter, is that the linear speed of the liner, and consequently the stock material delivered from the supply roll, will vary if the control is based upon the speed of the take-up reel. The linear speed of the liner constantly changes due to the changing diameter of the take-up reel as it accumulates the stock liner thereon.
The most pertinent known examples of prior art server systems are disclosed in the following patents discussed below.
U.S. Pat. No. 1,959,418 discloses a winder for sheet material which includes an endless belt guided around rollers. A belt conveyor is provided for feeding strips of the material, and a plurality of bands are provided between adjacent knives.
U.S. Pat. No. 2,480,704 discloses a server for tire building machines in which a drum and fabric supply device is mounted rearwardly of the tire building drum. The server includes a frame having a base in a vertical standard, and arms are adapted to receive liner reels. The reels are positioned directly over rollers and are supported on the rollers by gravity. The liner wind-up reels are frictionally driven at a peripheral speed equal to that of the fabric in order to uniformly wind the liners. The apparatus is provided with means for automatically stopping the driving after a predetermined amount of fabric has been fed from rolls.
U.S. Pat. No. 2,755,028 discloses an apparatus for handling tire-ply material after manufacture and prior to assembly. The apparatus includes a pair of reels, each of which has a substantial length of liner stored thereon. At the end of the loading operation one of the reels will hold a liner with ply-stock interleaved therewith. The reels are rotatably driven by friction drive means and when the liner diameter on each of the take-up reels reaches a desired maximum size, a limit switch is actuated to stop the driving motor.
U.S. Pat. No. 3,293,101 discloses a tire fabric transfer mechanism which includes a photocell tracking unit which actuates a piston/cylinder assembly. The photocell unit maintains alignment of the edge of the stock material being delivered. The liner is removed from the stock roll at the same rate as the fabric is removed from the roll. Rolls of stock and liner material are mounted within receptacles and delivered into position when necessary.
U.S. Pat. No. 3,623,677 discloses an apparatus for automatically delivering successive lengths of ply-forming material from supply rolls to a tire building drum. The leading edges of the material are positioned at a predetermined proximity to the drum in an automatic fashion. The tire server includes a driving assembly with an electric motor to unwind the stock from the supply roll. A photocell unit is mounted on the frame and upon a "free-loop" reaching a maximum downward extent it will intercept a light beam to deenergize the feed mechanism to maintain a predetermined amount of material in the free loop.
U.S. Pat. No. 4,457,802 discloses an apparatus for conveying and shaping rubber sheet material which includes a pair of serving mechanisms. Rubber sheet is provided in a stock roll with an intervening liner and is driven by a motor in accordance with the amount of rubber material accumulating in a festoon portion of a "free loop" of stock material.
U.S. Pat. No. 4,540,131 discloses a roll sheet delivery and transfer mechanism in which a liner windup roller is driven by a touch roller which is in contact with the outer surface of the liner windup roller. In this mechanism the sheet material is delivered from the rolled sheet together with the liner and when the front of the sheet material arrives at a terminal end of the conveyor it is transferred to a feed conveyor by a push-down roller which is actuated by a photoelectric detection device.
Russian Pat. No. 897574 discloses a supply and application machine for rubber tread section blank which includes a transporting apparatus and a drive mechanism for moving a transporter towards the assembly drum. The apparatus also includes a length checking mechanism to determine the position of the rear edge of the blank to determine whether any cutting is required.
However, none of these prior art patents discloses the use of spaced timing belts for hugging and driving the liner onto a takeup reel to maintain the liner moving at a controlled and measureable liner speed by eliminating the formation of a free loop in the sheet material for accurately regulating the length of sheet material being delivered to a work station, or discloses the use of a camera with feedback to a motor controller, which subsequently commands the server drive to make any required adjustment of the stock material edge position.